ASTM B338 Titanium Heat Exchanger Tube: Complete Specification Guide | Grade 1, 2, 7, 12

Published by Engineering Team, Shaanxi Qianyi Tuoda Technology Co., Ltd on 2026-10-27

ASTM B338 Titanium Heat Exchanger Tube: Complete Specification Guide

Reviewed by the Engineering Team, Shaanxi Qianyi Tuoda Technology Co., Ltd.

1. Scope and Coverage

ASTM B338 covers seamless and welded titanium and titanium alloy tubes for condensers and heat exchangers. This is the single most specified standard for titanium tubing in chemical processing, desalination, power generation, and marine service.

The standard applies to commercially pure titanium (Grades 1, 2, 3, 7, 11) and alloy grades (Grades 9, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 24, 25, 26, 27, 28, 29, 30, 31, 33, 34, 35, 36, 37, 38). For industrial heat exchanger procurement, however, Grades 1, 2, 7, and 12 account for over 95% of orders.

B338 defines chemical composition, tensile properties, flattening test, flaring test (for seamless), reverse flattening test (for welded), non-destructive examination (eddy current or ultrasonic), and dimensional tolerances. It does not cover:

• General corrosion-resistant pipe (ASTM B861 / B862)
• Fittings (ASTM B363)
• Forgings (ASTM B381)
• Plate and sheet (ASTM B265)

Critical distinction: B338 is for heat exchanger and condenser tubes — thin-wall, typically 0.5–3.0mm wall, supplied in straight lengths (up to 24m) or U-bent. It is not a piping standard. Specifying B338 for process pipe is a category error; use B861 (seamless pipe) or B862 (welded pipe) instead.

2. Grade Selection by Application

Cost index relative to Gr2 tube; actual pricing varies with Pd/Mo/Ni surcharges and order volume.

3. Chemical Composition

ASTM B338 Table 1 lists composition limits. For the four dominant heat exchanger grades:

Procurement note: For Grade 7, the Pd content is the only compositional difference from Grade 2. A Mill Test Certificate (MTR) must show Pd in the 0.12–0.25% range — visual inspection cannot confirm this. Always request PMI (XRF) verification on Gr7 tubes, especially for critical service.

4. Mechanical Properties

Values per ASTM B338-21. Yield strength measured at 0.2% offset; elongation on 50mm gauge length.

Key observation for tube buyers: Grade 7 has identical strength to Grade 2 (345/275 MPa). The Pd addition does not increase strength — it improves corrosion resistance in reducing environments. Specifying Gr7 for a seawater application where Gr2 is adequate wastes money; specifying Gr2 for a wet-chlorine or reducing-acid application where Gr7 is required risks premature tube failure. The selection decision is purely corrosion-driven, not strength-driven.

5. Dimensional Tolerances

B338 defines tolerances for outside diameter (OD), wall thickness, length, and straightness. For procurement, the critical values are:

Critical procurement note: B338 tolerances are the minimum. For heat exchanger tube bundles, tighter OD and wall tolerances are often required to ensure uniform flow distribution and proper fit in tube sheets. [FILL: your shop's actual OD control capability, e.g. "±0.05mm on OD 12–25mm tubes"]

For U-bent tubes (B338 permits U-bending after straight-tube production), the leg length tolerance and bend radius must be specified on the PO. Minimum bend radius is typically 2×OD for Gr2/Gr7; tighter bends risk wall thinning or cracking.

6. Manufacturing Route: Seamless vs Welded

B338 covers both seamless and welded tubes. The choice affects cost, availability, and certain performance characteristics:

Procurement decision: For most heat exchanger and condenser service, welded tubes per B338 are acceptable and cost-effective. Seamless is specified when the tube wall is subject to external pressure collapse (e.g., bayonet tubes) or when the service fluid is highly aggressive on the OD and any weld discontinuity is unacceptable. [FILL: your available seamless vs welded size ranges and lead times]

7. Procurement Checklist: How to Write a B338 PO

A complete purchase order citing ASTM B338 should include all eight fields:

1. Standard + grade: "ASTM B338 Grade 2 (UNS R50400)" or "ASTM B338 Grade 7 (UNS R52400)"
2. Manufacturing route: Seamless (SMLS) or Welded (WLD)
3. Dimensions: OD × wall thickness × length (e.g., "25.4mm OD × 1.2mm wall × 6000mm long")
4. Quantity: Number of tubes (or total linear meters)
5. Condition: Annealed (standard), stress-relieved, or bright annealed
6. Surface finish: Pickled (standard), bright annealed, or passivated per ASTM A967
7. Testing: Eddy current (mandatory per B338), hydrostatic (optional but recommended for critical service), PMI for Gr7/Gr12
8. Certification: EN 10204 3.1 MTR minimum; 3.2 if required by project. UT report for welded tubes.

Common failure: Specifying "B338 titanium tube 1 inch × 0.049 inch" without grade, manufacturing route, or length. The supplier can legally deliver Grade 1 welded tube in random lengths — which may not meet your heat exchanger design. Always complete all eight fields.

Additional fields for critical service:

• U-bend dimensions (leg length, bend radius, straight tangent length)
• Tube-end preparation (square cut, deburred, expanded end)
• Packaging: bundle wrapping, end caps, wooden crate, moisture barrier
• Traceability: heat number marking on each tube (stamping or laser)

8. Frequently Asked Questions

This guide is maintained by the Engineering Team at Shaanxi Qianyi Tuoda Technology Co., Ltd. Data sourced from ASTM B338-21. For procurement support, contact sales@sxqytd.com.